This invention relates to a device adapted to be secured to a movable structure such as the wrist of a robot, and to control a tool supported by the device so as to interpolate a locus of a circular or noncircular configuration.
In the case of producing a body portion of an automobile or parts to be installed thereon, it is required to form numerous holes of circular, oval, rectangular and other configurations for inserting machine screws, bolts and other instruments through these holes. Although it is an ordinary practice to form these holes by means of a punch press and the like, in the case of 3-dimensional products such as a body portion of the automobile, setting of the punch press is not easy, and furthermore, the configuration and the size of the products are different due to model change and different type of the motor vehicle. For this reason, the application of the punch press is not easy, and therefore use of a robot for forming these holes is now prevalent. FIG. 18 shows a robot adapted to form these holes. The robot has a plurality of arms such as those designated by 1a and 1b having a number of degrees of freedom corresponding thereto. A tool 2 is supported by a wrist of the robot provided subsequent to the last arm. The tool 2 may be any of a laser gun, plasma gun, water-jet gun and the like, a small hole 4 is thereby formed through a work 3 of a 3-dimensional configuration according to an arc-interpolation procedure under the control of a robot controller operating at a high speed. Holes of a polygonal shape or an elongated circular and rectangular shape may also be produced by combining a linear interpolation, circular interpolation and the like.
However, the locus interpolation controlled by the robot exhibits difficulties in its slow operation speed and time delay caused by the following reasons.
(1) The peripheral speed required for forming these holes, which is determined by the operational characteristics of the tool, is much faster than the control speed of the robot.
(2) The diameter of the hole to be formed is in a range of 4-20 mm, and hence arc-interpolation is extremely difficult.
(3) In a case of a construction where the tool is controlled in a noncircular locus interpolation with respect to two coordinate axes (such as X-Y tables) perpendicular to each other, the size of the unit becomes large, cost of the production becomes high, and installation of cables operating the tool and motors becomes difficult.